In the year 2021, mankind was defeated by Gastrea, a parasitical virus, and was forced to live within a wall made of Baranuim monoliths, a metal that is able to subdue Gastrea. Soon, the "Cursed Children" were discovered: children born infected with the Gastrea virus who possess superhuman abilities. Due to the Gastrea virus' intervention, the Cursed Children could only be female. Civil Securities are formed to specialize fighting against Gastrea, operating with the pair of an Initiator, who are cursed children, and a Promoter, serving to lead the cursed children. Ten years after the war, Rentarou Satomi, a high school student and Civil Security member, and his Initator Enju Aihara, receive a secret mission to prevent Tokyo's destruction.